Support interstitials with no primary button

components/security_interstitials/content/security_interstitial_controller_client.cc

Index: components/security_interstitials/content/security_interstitial_controller_client.cc
diff --git a/components/security_interstitials/content/security_interstitial_controller_client.cc b/components/security_interstitials/content/security_interstitial_controller_client.cc
index 150505e5f5ad71b93849ad88951833276703d720..5bca261406fe4a27757eec0d16aceaf0d6b0dee6 100644
--- a/components/security_interstitials/content/security_interstitial_controller_client.cc
+++ b/components/security_interstitials/content/security_interstitial_controller_client.cc
@@ -99,4 +99,9 @@ void SecurityInterstitialControllerClient::LaunchDateAndTimeSettings() {
   NOTREACHED();
 }
 
+// For testing, should be set in the WV controller.

[felt, 2017/05/05 00:31:14]

I'm confused by this comment

[edwardjung, 2017/05/05 10:24:24]

Wasn't sure whether this was going to be hard coded for the desktop. I've
changed this.

+bool SecurityInterstitialControllerClient::CanGoBack() {
+  return true;
+}
+
 }  // namespace security_interstitials